The invention relates to a method for regulating the fuel injection in an internal combustion engine, to which combustion air is fed through an intake tract, in which two final control elements which are connected in series in the intake tract and in each case control the air mass flow through the intake tract are controlled in respect of their position, whereby an air mass flow into the intake tract and also an induction manifold pressure prevailing in the intake tract are measured and measurement values are formed in the process.
In particular in the case of an internal combustion engine having external fuel/air mixing a method is known for controlling the combustion air mass flow and thus the fuel injection in the combustion chambers of the internal combustion engine by way of a final control element provided in the intake tract. Normally this final control element takes the form of a throttle valve which can be used to stop the cross-section of the intake tract. The position of the throttle valve then has a direct effect on the fuel injection. If the throttle valve is not fully open, then the air drawn in by the internal combustion engine is throttled and the torque delivered by the internal combustion engine is thus reduced. This throttle effect depends on the position and thus on the cross-section of opening of the throttle valve. When the throttle valve is fully open, the maximum torque is delivered by the internal combustion engine.
In order to achieve optimum control of the throttle valve, the latter is actuated by an actuator with position feedback. In this situation, a control unit is provided which calculates the required opening for the throttle valve by taking into consideration the current operational state of the internal combustion engine and controls the throttle valve actuator. To this end, an accelerator pedal position is evaluated by way of a pedal sensor.
During operation of the internal combustion engine, particular importance is attached to the determination of the air mass flowing into the cylinders of the internal combustion engine. EP 0 820 559 B1 proposes a model-based method in this respect, in which a variable which is characteristic of the fuel injection, namely the air mass flow or the induction manifold pressure, is measured and used in a model structure for more precise determination of the fuel injection. As a result, it is possible to exactly implement a desired fuel injection, which has been calculated from a requested torque for example, by means of a corresponding throttle valve setting.
In order to keep the losses occurring at the throttle valve as small as possible, a method is known whereby inlet valves of an internal combustion engine are capable of being operated with variable valve lift. The inlet valves then open with a settable valve lift such that it is possible to dispense with the actuation of the throttle valve at least in certain operational phases of the internal combustion engine. The fuel injection for the internal combustion engine is then controlled exclusively by way of the setting for the valve lift.
Both in order to obtain the lowest possible fuel consumption and in order to achieve a transition which is as imperceptible as possible and thus convenient between fully unthrottled operation, in other words operation of the internal combustion engine with fuel injection regulated exclusively by way of the valve lift adjustment, and conventional operation, the aim is to achieve as smooth a transition as possible with overlapping effects of valve lift control and throttle valve control.
The object of the invention is therefore to set down a method for regulating fuel injection in an internal combustion engine in which two final control elements which are connected in series in the intake tract and in each case control the air mass flow through the intake tract are coordinated with one another and can be used for regulating fuel injection.